Charging device, image forming unit, and image forming device

Abstract

To suppress occurrence of charging unevenness attributable to the vibration of a control electrode, as compared with the case where a plurality of connecting parts constituting a control electrode are evenly arranged along the axial direction.SOLUTION: A charging device comprises discharge wires 121a, 121b, 121c, and a grid electrode 122 located between the discharge wires 121a, 121b, 121c and a photoreceptor drum. The grid electrode 122 includes linear conductors 122f, 122f, etc., arranged along the longer direction L of the charging device and a plurality of connecting parts 122b, 122g, etc., for connecting the linear conductors 122f, 122f, etc., with each other along the width direction W of the charging device. When trisected into a middle part 400 and both end parts 401, 402 along the longer direction L of the charging device, the plurality of connecting parts 122b, 122g, etc., are located more in the middle region than in regions at both ends of the grid electrode 122.SELECTED DRAWING: Figure 14

Description

[Technical Field]

[0001] The present invention relates to a charging device, an image forming unit, and an image forming apparatus. [Background technology]

[0002] Conventionally, techniques relating to charging devices have already been proposed, for example, as disclosed in Patent Documents 1 and 2.

[0003] In Patent Document 1, the grid electrode has multiple regions with different opening pitches in the rotation axis direction, and of the multiple regions, the region facing the discharge electrode has a smaller opening pitch than the non-facing region.

[0004] In Patent Document 2, the potential control plate has three or more structural lines arranged in the circumferential direction of the charged body and extending linearly along the axial direction of the charged body, and a plurality of connecting portions arranged in the axial direction of the charged body and connecting parts of the three or more structural lines that are continuous in the circumferential direction of the charged body, and the structural lines connecting one connecting portion to another connecting portion among the plurality of connecting portions are configured so that at least a portion of them is different. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2013-045060 A [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-203364 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to suppress the occurrence of uneven charging due to vibration of the control electrode compared to when the multiple connecting portions that make up the control electrode are evenly arranged along the axial direction. [Means for solving the problem]

[0007] The invention described in claim 1 comprises a discharge electrode, a control electrode disposed between the discharge electrode and a body to be charged by the discharge electrode; Equipped with The control electrode is a plurality of linear conductors arranged so as to intersect with the rotation direction of the body to be charged at an arbitrary angle; a plurality of connecting portions which are members connecting the linear conductors along the rotation direction of the body to be charged, and which are arranged more in a central region than in both end regions in a direction intersecting the rotation direction of the body to be charged; The charging device has the following.

[0008] The invention described in claim 2 comprises a discharge electrode, a control electrode disposed between the discharge electrode and a body to be charged by the discharge electrode; Equipped with The control electrode is a plurality of linear conductors arranged so as to intersect with the rotation direction of the body to be charged at an arbitrary angle; a plurality of connecting portions which are members connecting the linear conductors along the rotation direction of the body to be charged, and which are arranged in a facing region where the discharge electrode and the control electrode face each other in greater numbers than in a non-facing region where the discharge electrode and the control electrode do not face each other in the rotation direction of the body to be charged; The charging device has the following.

[0009] The invention described in claim 3 is the charging device described in claim 1, wherein the plurality of connecting portions connect adjacent ones of the plurality of linear conductors to each other.

[0010] The invention described in claim 4 is characterized in that the plurality of connecting portions are 4. The charging device according to claim 3, wherein the density of the connecting portions is highest in the central region of the control electrode in a direction intersecting the rotation direction of the charged body, and the density of the connecting portions is gradually decreased toward both ends of the control electrode.

[0011] The invention described in claim 5 is the charging device described in claim 1, wherein the plurality of connecting portions are arranged including a non-opposing area where the discharge electrode and the control electrode do not face each other.

[0012] The invention described in claim 6 is characterized in that the plurality of connecting portions are 6. The charging device according to claim 5, wherein the density of connecting portions in an opposing region where the discharge electrode and the control electrode are opposed to each other is higher than the density of connecting portions in a non-opposing region where the discharge electrode and the control electrode are not opposed to each other in a direction intersecting the rotation direction of the charged body.

[0013] A seventh aspect of the present invention is the charging device according to the first aspect, wherein the control electrode has a uniform aperture ratio along a direction intersecting with the rotation direction of the body to be charged.

[0014] The invention described in claim 8 is characterized in that the plurality of connecting portions are 8. The charging device according to claim 7, wherein the line width of the connecting portion at the center of the control electrode is narrower than the line width of the connecting portion at both end regions in a direction intersecting the rotation direction of the member to be charged.

[0015] A ninth aspect of the present invention is the charging device according to the first aspect, wherein a plurality of the discharge electrodes are arranged along the rotation direction of the body to be charged.

[0016] A tenth aspect of the present invention is the charging device according to the ninth aspect, wherein the discharge electrode has a higher applied voltage on the most upstream side along the direction of rotation of the body to be charged than on the other sides.

[0017] The invention described in claim 11 includes the charging device according to any one of claims 1 to 10, This is an image forming unit that is detachably attached to an image forming apparatus.

[0018] The invention described in claim 12 comprises an image holding means, a charging means for charging the surface of the image holding means; an electrostatic latent image forming means for forming an electrostatic latent image on the surface of the image holding means charged by the charging means; Equipped with The image forming apparatus uses the charging device according to any one of claims 1 to 10 as the charging means. [Effects of the Invention]

[0019] According to the invention described in claim 1, the occurrence of uneven charging due to vibration of the control electrode can be suppressed compared to when the multiple connecting portions constituting the control electrode are evenly arranged along the axial direction.

[0020] According to the invention described in claim 2, the occurrence of uneven charging due to vibration of the control electrode can be suppressed compared to when the multiple connecting portions constituting the control electrode are arranged in equal numbers in the non-opposing area where the discharge electrode and the control electrode do not face each other and in the facing area where the discharge electrode and the control electrode face each other.

[0021] According to the invention as recited in claim 3, vibration of the linear conductors can be suppressed more effectively than when adjacent linear conductors among the linear conductors are not connected to each other.

[0022] According to the invention described in claim 4, the occurrence of vibration in the linear conductor can be effectively suppressed compared to when multiple connecting portions are arranged so that the density is equal in the central region of the control electrode and the regions at both ends of the control electrode in a direction intersecting the rotation direction of the charged body.

[0023] According to the invention described in claim 5, vibration of the linear conductor can be effectively suppressed compared to when multiple connecting portions are arranged only in the opposing area where the discharge electrode and the control electrode face each other.

[0024] According to the invention described in claim 6, the multiple connecting portions can effectively suppress vibration of the linear conductor compared to when the density of the connecting portions in the non-opposing region where the discharge electrode and control electrode do not face each other in a direction intersecting the rotation direction of the charged body is equal to the density of the connecting portions in the facing region where the discharge electrode and control electrode face each other.

[0025] According to the invention described in claim 7, the control electrode can suppress unevenness in the charging potential along the axial direction of the charged body compared to when the aperture ratio along the axial direction of the charged body is different.

[0026] According to the invention described in claim 8, the aperture ratio of the multiple connecting portions can be easily set compared to when the line width of the connecting portions in the regions at both ends of the control electrode in the direction intersecting the rotation direction of the charged body is equal to the line width of the connecting portions in the central portion.

[0027] According to the invention as set forth in claim 9, the charging ability can be improved compared to when a single discharge electrode is used.

[0028] According to the invention described in claim 10, the discharge electrode can improve the charging characteristics of the body to be charged compared to when the applied voltage is set high except for the most upstream side along the rotation direction of the body to be charged.

[0029] According to the invention described in claim 11, the occurrence of uneven charging caused by vibration of the control electrode can be suppressed compared to when the charging device described in any of claims 1 to 10 is not provided.

[0030] According to the invention described in claim 12, compared to when a charging device described in any of claims 1 to 10 is not used as a charging means, it is possible to suppress the occurrence of uneven charging caused by vibration of the control electrode, thereby improving image quality. [Brief explanation of the drawings]

[0031] [Figure 1]1 is an overall configuration diagram showing an image forming apparatus to which a charging device according to a first embodiment of the present invention is applied; [Figure 2] 1 is a configuration diagram showing an image forming device of an image forming apparatus according to a first embodiment of the present invention; [Figure 3] 1 is a perspective view showing the configuration of an image forming unit according to a first embodiment of the present invention; [Figure 4] 1 is a perspective view showing the configuration of a unit main body of an image forming unit according to a first embodiment of the present invention; [Figure 5] 1 is a perspective view showing the configuration of a grid electrode of a charging device according to a first embodiment of the present invention; [Figure 6] FIG. 3 is a configuration diagram showing a control unit for a grid electrode. [Figure 7] FIG. 2 is a diagram illustrating the principle of a charging device. [Figure 8] 1 is a perspective view showing the configuration of a grid electrode of a charging device according to a first embodiment of the present invention; [Figure 9] 1 is a perspective view showing the configuration of a charging device according to a first embodiment of the present invention. [Figure 10] 1 is a perspective view showing an insulating block at the rear end of a charging device according to a first embodiment of the present invention; [Figure 11] 1 is a perspective view showing an insulating block at the front end of a charging device according to a first embodiment of the present invention; [Figure 12] FIG. 2 is a structural diagram showing a tension member. [Figure 13] FIG. 2 is a cross-sectional view showing a main part of an insulating block at the front end. [Figure 14] 1 is a plan view showing the configuration of a grid electrode of a charging device according to a first embodiment of the present invention. [Figure 15] 3 is a schematic view showing a facing region in the charging device according to the first embodiment of the present invention. FIG. [Figure 16] FIG. 10 is a plan view showing the configuration of a grid electrode of a charging device according to a second embodiment of the present invention. [Figure 17] FIG. 11 is a plan view showing the configuration of a grid electrode of a charging device according to a third embodiment of the present invention. [Figure 18]FIG. 10 is a plan view showing the configuration of a grid electrode of a charging device according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0032] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0033] [Embodiment 1] FIG. 1 is a schematic diagram showing the overall configuration of an image forming apparatus to which a charging device and an image forming unit according to a first embodiment of the present invention are applied.

[0034] <Overall configuration of image forming apparatus> The image forming apparatus 1 according to the first embodiment is configured as, for example, a color printer. As shown in FIG. 1 , the image forming apparatus 1 includes a plurality of image creating devices 10, an intermediate transfer device 20, a paper feeder 50, a fixing device 40, and the like. The plurality of image creating devices 10 form toner images developed with toner constituting a developer. The intermediate transfer device 20 holds each toner image formed by the image creating devices 10 and transports it to a secondary transfer position where the toner image is finally secondarily transferred onto a recording sheet 5, an example of a recording medium. The paper feeder 50 stores and transports the required recording sheet 5 to be supplied to the secondary transfer position of the intermediate transfer device 20. The fixing device 40 fixes the toner image on the recording sheet 5 secondarily transferred by the intermediate transfer device 20. Note that the two-dot chain lines in the figure indicate the main transport paths along which the recording sheet 5 is transported within the image forming apparatus 1.

[0035] The image forming device 10 is composed of four image forming devices 10Y, 10M, 10C, and 10K that are dedicated to forming toner images of four colors, yellow (Y), magenta (M), cyan (C), and black (K), respectively. These four image forming devices 10 (Y, M, C, K) are arranged in a horizontal row in the internal space of the image forming device 1.

[0036] As shown in FIG. 2, each image forming device 10 (Y, M, C, K) includes a rotating photosensitive drum 11, which serves as an example of a charge-receiving member and an image-holding device. Surrounding the photosensitive drum 11 are a charging device 12, which serves as an example of a charging device according to the first embodiment; an exposure device 13, which serves as an example of an electrostatic latent image forming device; a developing device 14; a primary transfer device 15; and a drum cleaning device 16. The charging device 12 charges the image-forming surface (image-holding surface) of the photosensitive drum 11 to a desired potential. The exposure device 13 irradiates the charged surface of the photosensitive drum 11 with light based on image information (signals) to form electrostatic latent images (for each color) with different potentials. The developing device 14 develops the electrostatic latent image with developer toner of the corresponding color (Y, M, C, K) to form a toner image. The primary transfer device 15 transfers each toner image to the intermediate transfer device 20. The drum cleaning device 16 removes and cleans the toner and other adhering matter remaining on the image bearing surface of the photosensitive drum 11 after the primary transfer.

[0037] The photoreceptor drum 11 has an image bearing surface formed on the circumferential surface of a grounded cylindrical or columnar substrate, with a photoconductive layer (photosensitive layer) made of a photosensitive material. The photoreceptor drum 11 is supported so that it rotates in the direction indicated by arrow A, which is an example of the movement direction, by a driving force transmitted from a driving means (not shown). As shown in FIG. 2, the surface shape of the photoreceptor drum 11 is curved into a circular shape with a required radius of curvature about the rotation axis.

[0038] The charging device 12 is a so-called scorotron charger disposed at a distance from the photosensitive drum 11. The scorotron charging device 12 has a higher charging capability for the photosensitive drum 11 than a roll-shaped charging roll. Therefore, the scorotron charging device 12 is particularly effective in a highly productive image forming apparatus 1 in which the rotation speed of the photosensitive drum 11, which determines the process speed, is increased. A charging voltage and a control voltage are supplied to the charging device 12. If the developing device 14 performs reversal development, the charging voltage is a voltage or current of the same polarity as the charging polarity of the toner supplied from the developing device 14. The configuration of the charging device 12 will be described in detail later.

[0039] The exposure device 13 is an LED print head. The LED print head forms an electrostatic latent image by irradiating the photosensitive drum 11 with light corresponding to image information using LEDs (Light Emitting Diodes) as a plurality of light-emitting elements arranged along the axial direction of the photosensitive drum 11. Note that the exposure device 13 may be one that deflects and scans laser light configured according to the image information along the axial direction of the photosensitive drum 11.

[0040] As shown in FIG. 2, each of the developing devices 14 includes a housing 140, which includes a developing roll 141, an agitation supply member 142, a developer supply roll 143, an agitation transport member 144, and a layer thickness regulating member 145. The housing 140 has an opening facing the photosensitive drum 11 and a developer storage chamber formed therein. The developing roll 141 holds the developer and transports it to a development area facing the photosensitive drum 11. The agitation supply member 142 is a screw auger or similar device that agitates the developer while feeding it past the developing roll 141. The developer supply roll 143 supplies the developer from the agitation supply member 142 to the developing roll 141. The agitation transport member 144 is a screw auger or similar device that agitates the developer while transporting it to the agitation supply member 142. The layer thickness regulating member 145 regulates the amount (layer thickness) of the developer held on the developing roll 141. In this developing device 14, a developing voltage is supplied from a power supply device (not shown) between the developing roll 141 and the photosensitive drum 11. As the four-color developer, for example, a two-component developer containing non-magnetic toner and magnetic carrier is used.

[0041] The primary transfer device 15 is a contact-type transfer device that includes a primary transfer roll that rotates in contact with the periphery of the photosensitive drum 11 via the intermediate transfer belt 21 and is supplied with a primary transfer voltage. The primary transfer voltage is a DC voltage that has a polarity opposite to the charge polarity of the toner and is supplied from a power supply device (not shown).

[0042] The drum cleaning device 16 is composed of a main body 160, a cleaning brush 161, a cleaning plate 162, a delivery member 163, and the like. The main body 160 is formed in the shape of a container with a portion open. The cleaning brush 161 is positioned so as to contact the circumferential surface of the photosensitive drum 11 after primary transfer with a required pressure to scrape off and clean any remaining toner and other adhering matter. The cleaning plate 162 is positioned so as to contact the circumferential surface of the photosensitive drum 11 with a required pressure to remove and clean any remaining toner and other adhering matter. The delivery member 163 is composed of a screw auger or the like that collects the toner and other adhering matter removed by the cleaning brush 161 and cleaning plate 162 and transports them to a collection system (not shown). The cleaning plate 162 is a plate-shaped member (e.g., a blade) made of a material such as rubber.

[0043] A discharge lamp 17 is disposed between the drum cleaning device 16 and the charging device 12. The discharge lamp 17 discharges the surface of the photosensitive drum 11 from which the drum cleaning device 16 has removed residual toner and other adhering matter by uniformly exposing the surface to light.

[0044] As shown in FIG. 1, the intermediate transfer device 20 is positioned vertically below each of the image forming devices 10. The intermediate transfer device 20 is primarily composed of an intermediate transfer belt 21, multiple belt support rolls 22-24, a secondary transfer device 30, and a belt cleaning device 25. The intermediate transfer belt 21 rotates in the direction indicated by arrow B while passing through a primary transfer position between the photosensitive drum 11 and the primary transfer device 15 (primary transfer roll). The multiple belt support rolls 22-24 support the intermediate transfer belt 21 so that it can rotate while maintaining a desired state from its inner surface. The secondary transfer device 30 is positioned on the outer peripheral surface (image bearing surface) of the intermediate transfer belt 21 supported by the belt support roll 24, and performs a secondary transfer of the toner image on the intermediate transfer belt 21 to the recording paper 5. The belt cleaning device 25 removes and cleans any remaining toner, paper dust, and other debris that remains on the outer peripheral surface of the intermediate transfer belt 21 after passing through the secondary transfer device 30.

[0045] The intermediate transfer belt 21 is an endless belt made of a material in which a resistance adjuster such as carbon black is dispersed in a synthetic resin such as polyimide resin or polyamide resin. The belt support roll 22 is configured as a drive roll that is rotationally driven by a drive device (not shown). The belt support roll 23 is configured as a surface-finishing roll that holds the image forming surface of the intermediate transfer belt 21. The belt support roll 24 is configured as an opposing roll that faces the secondary transfer device 30. The belt support roll 22 also functions as a support roll that supports the back surface of the belt cleaning device 25.

[0046] 1, the secondary transfer device 30 is a contact-type transfer device equipped with a secondary transfer roll 31. The secondary transfer roll 31 rotates in contact with the circumferential surface of the intermediate transfer belt 21 at a secondary transfer position, which is the outer circumferential surface of the intermediate transfer belt 21 supported by the belt support roll 24 in the intermediate transfer device 20, and a secondary transfer voltage is supplied to the secondary transfer roll 31 or the belt support roll 24 of the intermediate transfer device 20. A DC voltage having the same or opposite polarity as the charge polarity of the toner is supplied as a secondary transfer voltage from a power supply device (not shown).

[0047] The fixing device 40 is configured by arranging a heating rotor 42, a pressure rotor 43, and other components inside a housing 41. The housing 41 is formed with an inlet and outlet for the recording paper 5. The heating rotor 42 is formed in the form of a belt or roll that rotates in the direction indicated by the arrow and is heated by a heating means so that the surface temperature is maintained at a predetermined temperature. The pressure rotor 43 is formed in the form of a roll or belt that rotates in contact with the heating rotor 42 at a predetermined pressure and rotates substantially along the axial direction of the heating rotor 42. In this fixing device 40, the contact area between the heating rotor 42 and the pressure rotor 43 forms the fixing nip N where the required fixing process (heating and pressure) is performed.

[0048] The paper feed device 50 is disposed so as to be located below the intermediate transfer device 20. This paper feed device 50 is mainly composed of one (or more) paper containers 51 and delivery devices 52 and 53. The paper container 51 stores a stack of recording paper 5 of a desired size, type, etc. The delivery devices 52 and 53 deliver the recording paper 5 one sheet at a time from the paper container 51. The paper container 51 is provided so that it can be pulled out, for example, from the front side (the side that the user faces when operating) of the device main body (not shown).

[0049] Examples of the recording paper 5 include plain paper used in electrophotographic copiers and printers, thin paper such as tracing paper, and overhead projector sheets. To further improve the smoothness of the image surface after fixing, it is preferable that the surface of the recording paper 5 is as smooth as possible. Suitable examples of the recording paper 5 include coated paper in which the surface of plain paper is coated with a resin or the like, and so-called thick paper with a relatively high basis weight, such as art paper for printing.

[0050] Between the paper feed device 50 and the secondary transfer device 30, there are provided one or more pairs of paper transport rolls 54, 55 and a paper feed transport path 56. The paper transport rolls 54, 55 transport the recording paper 5 fed from the paper feed device 50 to the secondary transfer position. The paper feed transport path 56 is formed by a transport guide (not shown). The paper transport roll pair 55, which is disposed in the paper feed transport path 56 immediately before the secondary transfer position, is configured as, for example, a roll (registration roll) that adjusts the transport timing of the recording paper 5. Between the secondary transfer device 30 and the fixing device 40, there are provided one or more pairs of paper transport rolls 57, 58 and a paper transport path 59 for transporting the recording paper 5 fed from the secondary transfer device 30 after the secondary transfer to the fixing device 40. A paper discharge unit (not shown) is provided on the side of the image forming apparatus 1 to discharge the recording paper 5 fed from the fixing device 40 after the fixing.

[0051] The image forming apparatus 1 may be provided with a double-sided paper transport path (not shown) for forming images on both sides of the recording paper 5.

[0052] 1, reference numeral 100 indicates a control device that comprehensively controls the operation of the image forming apparatus 1. The control device 100 includes a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), which are not shown, as well as buses and communication interfaces that connect the CPU, ROM, etc.

[0053] <Configuration of image forming unit> 2, the image forming apparatus 1 according to the first embodiment includes a plurality of image forming units 200 corresponding to the respective imaging devices 10 (Y, M, C, K) in order to improve maintainability. Each image forming unit 200 is configured by integrating a plurality of members, including at least the photosensitive drum 11, from among the members constituting each imaging device 10. Each image forming unit 200 is individually detachable from the image forming apparatus 1.

[0054] In this embodiment 1, as shown in FIG. 2, the photosensitive drum 11, charging device 12, and drum cleaning device 16 are integrally configured as an image forming unit 200. Note that the charging device 12 may be configured to be detachable and separate from the photosensitive drum 11 and drum cleaning device 16. The image forming unit 200 is replaced when the photosensitive drum 11 and other components reach the end of their life. The image forming unit 200 is also replaced with a new one when a malfunction occurs in the charging device 12 or drum cleaning device 16. If the image forming unit 200 does not include the developing device 14, it is possible to use a common image forming unit 200 for all imaging devices 10.

[0055] As shown in FIG. 3, the image forming unit 200 includes a unit main body 201. The unit main body 201 has front and rear support portions 202 and 203 and a connecting portion 204. The front and rear support portions 202 and 203 rotatably support both axial ends of the photosensitive drum 11. The connecting portion 204 connects the front and rear support portions 202 and 203 to one side of the photosensitive drum 11. As shown in FIG. 4, the front and rear support portions 202 and 203 are provided with front and rear positioning portions 205 and 206 that position both longitudinal ends of the charging device 12. The front and rear positioning portions 205 and 206 are each provided with positioning holes 205a, 205b and 206a, 206b that position the charging device 12.

[0056] Curved portions 207 and 208 are provided on the front and rear support portions 202 and 203 of the unit main body 201. When the charging device 12 is attached, the curved portions 207 and 208 support the grid electrode 122 of the charging device 12 in a curved shape that follows the surface shape of the photosensitive drum 11. The curved portions 207 and 208 are formed in an arc shape that protrudes a required distance from the surface of the photosensitive drum 11, which is rotatably attached to the image forming unit 200. The height of the curved portions 207 and 208 determines the gap (DGS) between the surface of the photosensitive drum 11 and the grid electrode 122 of the charging device 12.

[0057] 3, the connecting portion 204 of the unit main body 201 also serves as the main body 160 of the drum cleaning device 16. A drive shaft 209 having a spiral convex portion 209a on its outer periphery is rotatably attached to the upper portion of the charging device 12. The drive shaft 209 drives a cleaning device (not shown) that cleans the charging device 12 along the axial direction of the photosensitive drum 11. An adapter portion 209b is provided at the rear end of the drive shaft 209 along the axial direction, to which driving force is transmitted from the image forming apparatus 1 when the image forming unit 200 is attached to the image forming apparatus 1.

[0058] The image forming unit 200 is configured to be insertable and removable from an opening provided on the front of the device body (not shown) of the image forming device 1 along a depth direction intersecting with the width direction of the image forming device 1. At this time, the image forming device 1 is in a state where a front cover (not shown) is open.

[0059] <Operation of image forming device> The basic image forming operation of the image forming apparatus 1 will be described below.

[0060] Here, the operation in a full-color mode in which the four image forming devices 10 are used to form a full-color image composed of a combination of toner images of four colors (Y, M, C, K) will be described.

[0061] The image forming apparatus 1 receives image information and command information requesting a full-color image forming operation (printing) from a personal computer, an image reading device, etc. (not shown). In response, the control device 100 starts the four image forming devices 10, the intermediate transfer device 20, the secondary transfer device 30, the fixing device 40, etc.

[0062] In each image forming device 10, as shown in FIG. 1, first, each photosensitive drum 11 rotates in the direction indicated by arrow A. Each charging device 12 charges the surface of each photosensitive drum 11 to a required polarity (negative polarity in the first embodiment) and potential. Next, exposure device 13 irradiates the surface of the charged photosensitive drum 11 with light emitted based on image signals obtained by converting the light into each color component (Y, M, C, K). As a result, electrostatic latent images of each color component, configured with a required potential difference, are formed on the surface of the photosensitive drum 11.

[0063] Next, each developing device 14 supplies toner of the corresponding color (Y, M, C, K) charged to the required polarity (negative polarity) from the developing roll 141 to electrostatically adhere to the electrostatic latent image of each color component formed on the photosensitive drum 11, thereby developing the image. Through this development, the electrostatic latent image of each color component formed on each photosensitive drum 11 is visualized as a toner image of four colors (Y, M, C, K) developed with the toner of the corresponding color.

[0064] Next, the toner images of each color formed on the photosensitive drum 11 of each image forming device 10 are transported to the primary transfer position. Then, the primary transfer device 15 performs primary transfer of the toner images of each color onto the intermediate transfer belt 21 of the intermediate transfer device 20, which rotates in the direction indicated by arrow B, in a state where the toner images are superimposed in order.

[0065] After the primary transfer is completed in each image forming device 10, the drum cleaning device 16 scrapes off any adhering matter to clean the surface of the photosensitive drum 11. After that, the charge removal lamp 17 uniformly exposes the surface of the photosensitive drum 11 to remove any static electricity. This prepares each image forming device 10 for the next image forming operation.

[0066] Next, the intermediate transfer device 20 holds the primarily transferred toner image and transports it to the secondary transfer position by the rotation of the intermediate transfer belt 21. Meanwhile, the paper feeder 50 sends out the required recording paper 5 to a paper feed path 56 in accordance with the image creation operation. In the paper feed path 56, a pair of paper transport rolls 55, which act as registration rolls, feeds and supplies the recording paper 5 to the secondary transfer position in accordance with the transfer timing.

[0067] At the secondary transfer position, the secondary transfer device 30 performs secondary transfer of the toner images on the intermediate transfer belt 21 all at once onto the recording paper 5. After the secondary transfer is completed in the intermediate transfer device 20, the belt cleaning device 25 removes and cleans the surface of the intermediate transfer belt 21 to remove any toner or other adhering matter remaining thereon after the secondary transfer.

[0068] Next, the recording paper 5 onto which the toner image has been secondarily transferred is peeled off from the intermediate transfer belt 21 and transported to the fixing device 40 via a paper transport path 59. In the fixing device 40, the recording paper 5 after the second transfer is introduced into and passes through the contact area between the rotating heating rotor 42 and pressure rotor 43. This performs the necessary fixing process (heating and pressure application) to fix the unfixed toner image onto the recording paper 5. Finally, the recording paper 5 after fixing is discharged to a paper discharge section, for example, installed on the side of the device main body (not shown).

[0069] By the above operation, the recording paper 5 is outputted on which a full color image formed by combining four color toner images is formed.

[0070] <Configuration of charging device> 2 and 3, the charging device 12 according to this embodiment 1 is disposed along the axial direction of the photosensitive drum 11, which is an example of a direction intersecting with the rotation direction A of the photosensitive drum 11. Here, the axial direction of the photosensitive drum 11 is the longitudinal direction of the charging device 12. In FIG. 3, the symbol L indicates the longitudinal direction of the charging device 12. W indicates the width direction of the charging device 12. H indicates the height direction of the charging device 12.

[0071] 3 shows a case where the charging device 12 is disposed directly above the photosensitive drum 11. In this case, the height direction H of the charging device 12 coincides with the vertical direction. However, the charging device 12 is not limited to being disposed directly above the photosensitive drum 11. The charging device 12 may be disposed at an angle along the circumferential direction of the photosensitive drum 11. In this case, the height direction H of the charging device 12 differs from the vertical direction.

[0072] As shown in FIG. 2, the charging device 12 broadly comprises a shield case 120 as an example of a housing, one or more (three in the illustrated example) discharge wires 121a, 121b, 121c as an example of a discharge electrode, and a grid electrode 122 as an example of a control electrode.

[0073] The shield case 120 is made of a metal such as stainless steel or aluminum. The shield case 120 functions as an opposing electrode when a high voltage is applied to the discharge wires 121a, 121b, and 121c to generate a corona discharge. The shield case 120 is formed in the shape of a rectangular parallelepiped elongated along the axial direction of the photosensitive drum 11, with an opening 123 that is open on the entire surface facing the photosensitive drum 11 (the bottom surface in the figure). The shield case 120 includes a top wall 120a, left and right side walls 120b and 120c, and two partition walls 120d. The top wall 120a is located at the upper end opposite the photosensitive drum 11. The left and right side walls 120b and 120c are bent downward from both ends of the top wall 120a along the width direction W toward the photosensitive drum 11. Partition wall 120d divides the space within shield case 120 along width direction W, which is the rotation direction A of photosensitive drum 11, in accordance with the number of discharge wires 121a, 121b, and 121c. Note that if there is only one discharge wire 121, partition wall 120d is not provided. The same high voltage as that applied to grid electrode 122 is applied to shield case 120, or it is grounded. The cylindrical or columnar conductive substrate of photosensitive drum 11 is grounded as described above.

[0074] An air outlet 120e is formed in the ceiling wall 120a of the shield case 120 to send air into the interior of the shield case 120. The air outlet 120e is opened in the center of the width direction W of the ceiling wall 120a over the entire length in the longitudinal direction L. Air is sent from the air outlet 120e toward the surface of the photosensitive drum 11. This removes discharge products such as ozone generated by corona discharge.

[0075] The discharge wires 121a, 121b, and 121c are made of tungsten, carbon tungsten, gold-plated tungsten, or the like. A negative high voltage of several kV to approximately 8 kV is applied to the discharge wires 121a, 121b, and 121c by a high-voltage power supply (not shown). The same high voltage is applied to all of the discharge wires 121a, 121b, and 121c. However, different high voltages may be applied to the discharge wires 121a, 121b, and 121c. For example, the highest high voltage is applied to the discharge wire 121a, which is located most upstream along the rotation direction A of the photosensitive drum 11. The other discharge wires 121b and 121c may be applied with the same lower voltage, or successively lower high voltages may be applied to the discharge wires 121b and 121c in that order. The reason why the applied voltage of the discharge wire 121a located most upstream along the rotation direction A of the photosensitive drum 11 is set to the highest value is because the charging potential of the photosensitive drum 11 is roughly determined by the discharge wire 121a.

[0076] The grid electrode 122 is arranged in an opening 123 of the shield case 120 facing the photosensitive drum 11, in a state curved in an arc to follow the surface shape of the photosensitive drum 11. A high voltage approximately equal to the desired potential is applied to the grid electrode 122, for example, by a high-voltage power supply (not shown), in order to achieve the desired charging potential of the photosensitive drum 11. Note that the grid electrode 122 does not necessarily have to be arranged in a curved state to follow the surface shape of the photosensitive drum 11; it may be bent to follow the surface shape of the photosensitive drum 11, or may be formed in a flat shape.

[0077] As shown in FIG. 5, the grid electrode 122 is formed into a thin, elongated rectangular flat plate corresponding to the opening 123 of the shield case 120 by etching or pressing a thin plate-like member made of a metal such as tungsten, carbon tungsten, or gold-plated tungsten. The grid electrode 122 integrally includes a control unit 122a and connecting units 122b and 122c. The control unit 122a is provided over the entire area of ​​the grid electrode 122 except for both ends along the longitudinal direction L. As shown in FIG. 3, the control unit 122a of the grid electrode 122 has a length along the axial direction of the photosensitive drum 11 equal to the image forming area of ​​the photosensitive drum 11. The connecting units 122b and 122c are provided at both ends along the longitudinal direction of the control unit 122a. Between the control portion 122a and the connecting portions 122b and 122c, there are provided short strip-shaped boundary portions 122d along the longitudinal direction L. As shown in Fig. 6, the grid electrode 122 may be provided with slightly wider strip-shaped edge portions 122e at both ends along the width direction W.

[0078] 6(a), the control section 122a of the grid electrode 122 is formed by arranging a plurality of narrow, linear conductors 122f, 122f, ... parallel to one another in the longitudinal direction L at a required density along the width direction W. Also, the control section 122a of the grid electrode 122 is formed by arranging a plurality of narrow, linear conductors 122f, 122f, ... parallel to one another in a required density and tilted along a direction intersecting the longitudinal direction L, as shown in FIG. 6(b). The control section 122a has minute gaps G formed between the plurality of linear conductors 122f, 122f, ... uniformly along the width direction W and the longitudinal direction L.

[0079] As shown in Fig. 7, the control unit 122a of the grid electrode 122 applies a high voltage to the discharge wires 121a, 121b, and 121c to generate corona discharge, thereby causing charged particles such as ions to adhere to the surface of the photosensitive drum 11 through gaps G formed between the narrow, linear conductors 122f, 122f, ..., thereby charging the surface of the photosensitive drum 11. The control unit 122a of the grid electrode 122 also controls the charging potential of the photosensitive drum 11 through the action of an electric field formed by the voltage applied to the control unit 122a. For convenience, Fig. 7 shows the surface of the photosensitive drum 11 and the grid electrode 122 as flat surfaces.

[0080] 5, the connecting portions 122b and 122c of the grid electrode 122 are configured so that trapezoidal frames protrude toward the ends at both ends along the longitudinal direction L. The connecting portions 122b and 122c are fixed in a tensioned state by being locked by locking portions provided on an insulating block, which will be described later.

[0081] The connecting portions 122b and 122c of the grid electrode 122 may be formed by arranging multiple sets of loop-shaped connecting portions 122b', 122c', 122b'', and 122c'' along the width direction W, as shown in FIG. 8.

[0082] 9, the charging device 12 includes a guide member 124, front and rear insulating blocks 125 and 126, and a mounting member 127. The guide member 124 is provided along the longitudinal direction on the surface of the shield case 120 opposite the photosensitive drum 11 (the lower surface in the figure). The front and rear insulating blocks 125 and 126 are respectively disposed at both ends of the shield case 120 along the longitudinal direction L. The mounting member 127 is provided at the front end of the front insulating block 125, which is disposed on the front side of the image forming apparatus 1.

[0083] The guide member 124 is formed into a long, thin flat plate shape from synthetic resin or the like. Two guide protrusions 124a, 124b are provided on both ends along the longitudinal direction of the outer surface of the guide member 124 to guide the charging device 12 when it is attached to the image forming apparatus 1. Of the two guide protrusions 124a, 124b, the guide protrusion 124b located on the rear side of the image forming apparatus 1 is formed longer than the guide protrusion 124a located on the front side of the image forming apparatus 1.

[0084] The insulating blocks 125, 126 at the front and rear ends are made of a single or multiple insulating members made of synthetic resin. The insulating blocks 125, 126 are fixed to both ends of the shield case 120 in the longitudinal direction L by means of snap engagement or the like. Three discharge wires 121a, 121b, 121c and a grid electrode 122 are stretched between the insulating blocks 125, 126 at the front and rear ends. One end of each of the discharge wires 121a, 121b, 121c is fixed to one of the insulating blocks 125, 126 at the front and rear ends, and the other end is fixed to the other insulating block 125 with a required tension applied via an elastic member such as a coil spring.

[0085] As shown in Figure 10, the rear insulating block 126 is provided with a curved holding portion 126a and multiple locking claws 126b, 126b.... The holding portion 126a holds the rear end of the grid electrode 122 by deforming it into a curved shape that matches the surface shape of the photosensitive drum 11. The multiple locking claws 126b, 126b... lock and secure the connecting portion 122c of the grid electrode 122. In addition, the tip of the rear insulating block 126 is provided with a semi-cylindrical and rectangular tubular current-carrying portion 126c. The current-carrying portion 126c incorporates multiple current-carrying electrodes (not shown) for applying current to the shield case 120, the discharge wires 121a, 121b, 121c, and the grid electrode 122, respectively. When the charging device 12 is attached to the image forming apparatus 1, the conductive portion 126c of the insulating block 126 at the rear end is connected to an electrode on the image forming apparatus 1 side. This allows current to flow through the shield case 120, the discharge wires 121a, 121b, and 121c, and the grid electrode 122.

[0086] Positioning pins 126d, 126d are provided to protrude longitudinally toward the rear side of the insulating block 126 at the rear end. As shown in Fig. 4, the positioning pins 126d, 126d are fitted into positioning holes 206a, 206b of a positioning portion 206 provided in a support portion 203 at the rear end of the image forming unit 200, thereby positioning the charging device 12.

[0087] 11, the insulating block 125 at the front end is provided with a curved holding portion 125a and a tensioning member 60. The holding portion 125a holds the front end of the grid electrode 122 by deforming it into a curved shape that conforms to the surface shape of the photosensitive drum 11. The tensioning member 60 applies tension to the grid electrode 122 by displacing the connecting portion 122b of the grid electrode 122 outward relative to the charging region of the grid electrode 122. The tensioning member 60 is attached to the insulating block 125 at the front end so as to be rotatable about a rotation axis that is disposed along the width direction W of the charging device 12.

[0088] 13, the holding portions 125a, 126a of the insulating blocks 125, 126 and the curved portions 207, 208 of the image forming unit 200 are arranged so as to protrude slightly toward the mating member relative to the tension position of the grid electrode 122. As a result, the shape and position of the grid electrode 122 are determined by the curved portions 207, 208 of the image forming unit 200.

[0089] 11, the insulating block 125 at the front end is provided with an upright wall 125d having an insertion hole 125c through which the connecting portion 122b of the grid electrode 122 is inserted. Furthermore, the upright wall 125d of the insulating block 125 is provided with positioning pins 125e, 125e (see FIG. 9) that protrude toward the charging region of the photosensitive drum 11 along the longitudinal direction L. As shown in FIG. 9, the positioning pins 125e, 125e position the front end of the charging device 12 along the width direction above the insertion hole 125c when the charging device 12 is attached to the image forming apparatus 1.

[0090] As shown in FIG. 12 , the tension member 60 attached to the insulating block 125 at the front end is formed by pressing or bending a metal sheet made of stainless steel or other metal, or by integral molding of synthetic resin. The tension member 60 includes a main body 601, a plurality of locking claws 602, 602..., pivotal support portions 603, 603, and a connecting portion 604. The main body 601 has a rectangular shape elongated horizontally along the width direction W of the charging device 12 when viewed from the front. The plurality of locking claws 602, 602... are provided at the top end of the main body 601 so as to protrude upward at required intervals. The pivotal support portions 603, 603 are bent perpendicularly from both ends of the main body 601 along the width direction. The connecting portion 604 is bent in the same direction as the pivotal support portions 603, 603 at the lower end of the main body portion 601, and connects one end of a coil spring 605 as an example of a biasing means.

[0091] The locking claws 602, 602... of the tension member 60 are arranged such that the locking claws 602, 602 at both ends in the width direction W are positioned close to the grid electrode 122. As a result, the locking claws 602, 602... are spaced approximately the same distance from the connecting pieces 122b', 122b" of the connecting portion 122b of the grid electrode 122, which is arranged in a curved shape.

[0092] Rotating shafts 603a, 603a are provided on the support portions 603, 603 of the tension member 60 so as to protrude toward both ends in the width direction. As shown in Fig. 13, the rotating shafts 603a, 603a of the tension member 60 are rotatably supported by support portions 125f provided inside the insulating block 125 at the front end.

[0093] As shown in Fig. 13, one end of a coil spring 605 is connected to the connecting portion 604 of the tension member 60. The other end of the coil spring 605 is fixed inside the insulating block 125. As a result, the tension member 60 is biased in the counterclockwise direction in the figure. Tension is applied by the coil spring 605 to the grid electrode 122 that is engaged with the engaging claws 602, 602, ... of the tension member 60.

[0094] The mounting member 127 of the charging device 12 is a member for mounting the charging device 12 in a fixed state when the charging device 12 is mounted to the image forming apparatus 1. As shown in Fig. 13, a fixed arm 127a biased in a counterclockwise direction by a spring 127b is rotatably attached to the mounting member 127. The charging device 12 is released from its mounted state with respect to the image forming apparatus 1 by manually gripping a release lever (not shown) provided on the mounting member 127 to rotate the fixed arm 127a in a clockwise direction.

[0095] 7, the charging device 12 configured as described above generates a corona discharge by applying a high voltage to the discharge wires 121a, 121b, and 121c. The charging device 12 charges the surface of the photosensitive drum 11 by causing charged particles such as ions generated by the corona discharge to pass through the grid electrode 122 and adhere to the surface. The control unit 122a of the grid electrode 122 controls the charging potential of the photosensitive drum 11 by the action of an electric field formed by the voltage applied to the control unit 122a.

[0096] At this time, in charging device 12, ionic wind 300 is generated from discharge wires 121a, 121b, and 121c toward the surface of photosensitive drum 11 located directly below. Furthermore, charging device 12 is configured to remove discharge products by sending air (air blow 301) toward the surface of photosensitive drum 11 from air blowing port 120e of shield case 120. Therefore, control unit 122a of grid electrode 122 stretched across opening 123 of shield case 120 is susceptible to vibration due to the influence of ionic wind 300 and air blow 301.

[0097] Furthermore, the charging device 12 is configured such that the control section 122a of the grid electrode 122 stretches a plurality of linear conductors 122f, 122f, ... along the longitudinal direction L. Therefore, the linear conductors 122f, 122f, ... of the grid electrode 122 tend to vibrate in resonance with driving force transmission means such as a driving motor that rotates the photosensitive drum 11, the developing device 14, or the intermediate transfer belt 21 of the image forming apparatus 1, or a driving gear that transmits driving force.

[0098] The charging device 12 had a technical problem in that when the linear conductors 122f, 122f, ... of the control unit 122a vibrate, charged particles such as ions passing through the control unit 122a are affected by the vibration, causing unevenness in the charging potential on the surface of the photosensitive drum 11.

[0099] Therefore, the charging device of this embodiment 1 is configured so that the control electrode has multiple straight conductors arranged so as to intersect with the rotation direction of the body to be charged at any angle, and multiple connecting portions that connect the straight conductors along the rotation direction of the body to be charged, with more connecting portions arranged in the central region than in the regions at both ends in the direction intersecting with the rotation direction of the body to be charged.

[0100] In addition, the charging device according to this embodiment 1 is configured to have a control electrode having a plurality of linear conductors arranged so as to intersect with the rotation direction of the body to be charged at any angle, and a plurality of connecting portions that connect the linear conductors along the rotation direction of the body to be charged, with more connecting portions arranged in the opposing regions where the discharge electrode and control electrode are opposing each other than in the non-opposing regions where the discharge electrode and control electrode are not opposing each other in the rotation direction of the body to be charged.

[0101] That is, as shown in FIG. 14, the charging device 12 according to this embodiment 1 uses, as the grid electrode 122, linear conductors 122f, 122f, ... arranged along the longitudinal direction L of the charging device 12, which is the axial direction of the photosensitive drum 11, and arranged parallel to each other with a small gap G between them along the width direction W of the charging device 12, which is the rotational direction of the photosensitive drum 11.

[0102] Furthermore, the grid electrode 122 of the charging device 12 includes a plurality of connecting portions 122g that connect the linear conductors 122f to one another along the width direction W of the charging device 12, which is the rotation direction of the photosensitive drum 11. The plurality of connecting portions 122g may connect the linear conductors 122f to one another along the width direction W of the charging device 12. In other words, the plurality of connecting portions 122g themselves do not necessarily need to be arranged along the width direction W of the charging device 12, but may also be arranged at an angle with respect to the width direction W of the charging device 12.

[0103] For example, when the charging device 12 is divided into three equal parts along the longitudinal direction L into a central portion 400 and both end portions 401 and 402, the multiple connecting portions 122g are configured to be arranged in greater numbers in the central region than in the end portion regions of the grid electrode 122. Note that in Figure 14, for convenience of explanation, the central portion 400 is shown slightly wider than the both end portions 401 and 402.

[0104] To explain further, among the multiple connecting portions 122g, 122g, ..., focus is placed on the uppermost linear conductor 122f1 along the width direction W of the charging device 12, and the second linear conductor 122f2 adjacent to the linear conductor 122f1. In this case, only one of the multiple connecting portions 122g, 122g, ... is provided in the regions of both end portions 401, 402 of the grid electrode 122, whereas three are provided in the central portion 400.

[0105] Similarly, attention is focused on the second straight conductor 122f2 from the uppermost straight conductor 122f1 along the width direction of the charging device 12, and the adjacent third straight conductor 122f3. Of the multiple connecting portions 122g, 122g, ..., only one is provided in the regions of both end portions 401, 402 of the grid electrode 122, while four are provided in the central portion 400.

[0106] The same is true for the other linear conductors 122f, with the multiple connecting portions 122g, 122g, . . . being provided more in the central portion 400 region than in the regions of the both end portions 401, 402 of the grid electrode 122.

[0107] In other words, the multiple connecting portions 122g are arranged so that the density is higher in the central portion 400 region than in the regions of the end portions 401, 402 of the grid electrode 122. Here, the density of the multiple connecting portions 122g refers to the number of connecting portions 122g arranged per unit length along the longitudinal direction L of the linear conductor 122f.

[0108] Furthermore, in the charging device 12 according to this embodiment 1, as shown in FIG. 14, the connecting portions 122g, 122g, ... of the grid electrode 122 are arranged more in the facing region 410 where the discharge wires 121a, 121b, 121c and the grid electrode 122 face each other than in the non-facing region 411 where the discharge wires 121a, 121b, 121c and the grid electrode 122 do not face each other.

[0109] 7, the facing region 410 where the discharge wires 121a, 121b, and 121c face the grid electrode 122 is not only the position directly below the discharge wires 121a, 121b, and 121c, but also the region directly affected by the ion wind 300 generated when a high voltage is applied to the discharge wires 121a, 121b, and 121c. The region directly affected by the ion wind varies depending on the voltage applied to the discharge wires 121a, 121b, and 121c and the distance between the discharge wires 121a, 121b, and 121c and the grid electrode 122. Here, the facing region 410 refers to the region where, when a perpendicular line 420 perpendicular to the surface of the grid electrode 122 is drawn from the discharge wires 121a, 121b, and 121c to the surface of the grid electrode 122, n linear conductors 122f exist on both sides of a position 421 where the perpendicular line 420 intersects with the surface of the grid electrode 122, as shown in FIG. The value of n depends on the arrangement density of the linear conductors 122f, 122f, ..., but is, for example, a value of 10 or less, and preferably a value of 5 or less. When the grid electrode 122 is curved, this is the case when a perpendicular line passing through the discharge wires 121a, 121b, 121c is drawn to a tangent to the surface of the grid electrode 122.

[0110] In the illustrated embodiment, as shown in FIG. 15, when a perpendicular line 420 is drawn from the discharge wires 121a, 121b, and 121c to the surface of the grid electrode 122, the opposing region 410 is a region where two linear conductors 122f exist on both sides of the position where the perpendicular line 420 intersects with the surface of the grid electrode 122.

[0111] To explain further, in the illustrated embodiment, as shown by the dashed line in Figure 14, the linear conductors 122f located in the opposing region 410 of the uppermost discharge wire 121a are a region in which a total of four linear conductors 122f exist, namely the third to sixth linear conductors 122f counting from the uppermost linear conductor 122f.

[0112] Similarly, in the illustrated embodiment, as shown in Figure 14, the linear conductors 122f located in the opposing area of ​​the discharge wire 121b located in the central portion are an area in which a total of four linear conductors 122f exist, from the topmost linear conductor 122f to the 10th to 13th linear conductors 122f.

[0113] Furthermore, in the illustrated embodiment, as shown in Figure 14, the linear conductors 122f located in the opposing area of ​​the discharge wire 121c located at the bottom are an area in which a total of four linear conductors 122f exist, namely the third to sixth linear conductors from the bottom of the lowest linear conductor 122f.

[0114] Focusing on the straight conductors 122f located in these opposing regions, for example, there are nine coupling portions 122g, 122g, ... that couple the third and fourth straight conductors 122f counting from the top straight conductor 122f. Also, there are ten coupling portions 122g, 122g, ... that couple the fourth and fifth straight conductors 122f counting from the top straight conductor 122f. Furthermore, there are nine coupling portions 122g, 122g, ... that couple the fifth and sixth straight conductors 122f counting from the top straight conductor 122f.

[0115] In contrast, when focusing on the linear conductors 122f located in the non-opposing region other than the opposing region, for example, there are five connecting portions 122g, 122g, ... connecting the first and second linear conductors 122f from the topmost linear conductor 122f, and there are six connecting portions 122g, 122g, ... connecting the second and third linear conductors 122f from the topmost linear conductor 122f.

[0116] As shown in FIG. 14, in the charging device 12 according to the first embodiment, the number of connecting portions 122g, 122g, ... of the grid electrode 122 is five or six in the non-opposing areas where the discharge electrode and the control electrode do not face each other, whereas the number of opposing areas where the discharge electrode and the control electrode face each other is nine or ten, which is approximately twice as many.

[0117] The same applies to the opposing regions facing the other discharge wires 121b and 121c.

[0118] Furthermore, in the charging device 12 according to this embodiment, attention is focused on the fourth and fifth straight conductors 122f from the topmost straight conductor 122f located in the facing region facing the discharge wire. As a result, the number of connecting portions 122g, 122g, ... connecting these straight conductors 122f to each other is two in the regions of both end portions 401, 402 of the grid electrode 122, but as many as six in the region of the central portion 400.

[0119] <Operation of the charging device> In the charging device according to this embodiment 1, it is possible to suppress the occurrence of uneven charging caused by vibration of the control electrode, compared to when the multiple connecting parts constituting the control electrode are arranged without taking into consideration the vibration characteristics of the control electrode, as follows.

[0120] In the image forming apparatus 1, as shown in FIG. 1, when an image is formed in each of the imaging devices 10 for yellow (Y), magenta (M), cyan (C), and black (K), the surface of each photosensitive drum 11 is uniformly charged to a required potential by the charging device 12.

[0121] At this time, in the charging device 12, a high voltage is applied to the discharge wires 121a, 121b, and 121c, and a required high voltage is applied to the grid electrode 122, as shown in FIG.

[0122] 7, in the charging device 12, vibrations are likely to occur in the linear conductors 122f, 122f, ... that make up the grid electrode 122. The reason for this is that, as described above, vibrations occur due to the influence of the ion wind 300 generated by applying a high voltage to the discharge wires 121a, 121b, 121c, the air blown in from the air outlet 120e of the shield case 120, and vibrations of the drive motors and drive force transmission means that drive the photosensitive drum 11, the developing device 14, the intermediate transfer device 20, and the like that are arranged around the charging device 12, which are transmitted via the frame, etc.

[0123] As shown in FIG. 14, the charging device 12 according to this embodiment 1 includes a plurality of connecting portions 122g, 122g, which connect adjacent linear conductors 122f, 122f, which constitute the grid electrode 122, along the width direction W of the charging device 12, which is the rotation direction of the photosensitive drum 11.

[0124] Furthermore, the multiple connecting portions 122g are arranged in greater numbers in the central portion 400 of the grid electrode 122 than in the regions of the end portions 401 and 402. In other words, the multiple connecting portions 122g are arranged with a higher density in the central portion 400, where vibrations are more likely to occur than in the regions of the end portions 401 and 402 of the grid electrode 122.

[0125] Furthermore, the multiple connecting portions 122g are more densely arranged in the facing region 410 where the discharge wires 121a, 121b, 121c and the grid electrode 122 face each other and vibrations are likely to occur due to the ion wind 300 from the discharge wires 121a, 121b, 121c, than in the non-facing region 411 where the discharge wires 121a, 121b, 121c and the grid electrode 122 do not face each other. In other words, the multiple connecting portions 122g are denser arranged in the facing region 410 where the discharge wires 121a, 121b, 121c and the grid electrode 122 face each other than in the non-facing region 411 where the discharge wires 121a, 121b, 121c and the grid electrode 122 do not face each other.

[0126] Therefore, in the charging device 12 according to the first embodiment, adjacent linear conductors 122f of the grid electrode 122 are connected by many connecting portions 122g in areas where vibration is likely to occur, thereby preventing or suppressing vibration in the linear conductors 122f. In addition, uneven charging caused by vibration of the linear conductors 122f of the grid electrode 122 can be prevented or suppressed.

[0127] Embodiment 2 16 is a structural diagram showing a charging device according to a second embodiment of the present invention. In the charging device according to the second embodiment, the control electrode is configured so that the aperture ratio is uniform along a direction intersecting the direction of rotation of the body to be charged.

[0128] That is, as shown in FIG. 16, the charging device 12 according to this embodiment 2 is configured so that the line width of the connecting portions 122g, 122g, ... varies depending on the arrangement density of the connecting portions 122g, 122g, ....

[0129] 7, the control unit 122a of the grid electrode 122 applies a high voltage to the discharge wires 121a, 121b, and 121c to generate corona discharge, causing charged particles such as ions to be deposited on the surface of the photosensitive drum 11 through gaps G formed between the narrow, linear conductors 122f, 122f, ..., thereby charging the surface of the photosensitive drum 11. The control unit 122a of the grid electrode 122 also controls the charging potential of the photosensitive drum 11 through the action of an electric field formed by the voltage applied to the control unit 122a.

[0130] Therefore, if the arrangement density of the multiple connecting portions 122g, 122g, ... that connect the linear conductors 122f, 122f, ... that make up the grid electrode 122 varies along the longitudinal direction L of the charging device 12, which is a direction that intersects with the rotation direction of the photosensitive drum 11, the opening ratio of the grid electrode 122 will no longer be uniform along the longitudinal direction L of the charging device 12.

[0131] Here, the aperture ratio (%) of the grid electrode 122 is (area of ​​gap G per unit area / unit area)*100.

[0132] When the aperture ratio of the grid electrode 122 is small due to the multiple connecting portions 122g, 122g, ... being arranged at a high density, the number of charged particles such as ions generated by the discharge wires 121a, 121b, 121c that pass through the gap G and head toward the surface of the photosensitive drum 11 decreases, and the proportion that flows to the grid electrode 122 increases.

[0133] On the other hand, if the aperture ratio of the grid electrode 122 is too large, the ability of the grid electrode 122 to compensate for the potential of the photosensitive drum 11 decreases, resulting in a state similar to that of a corotron, which is undesirable. Therefore, it is desirable that the aperture ratio of the grid electrode 122 be uniform and between 86% and 95%.

[0134] As shown in FIG. 16, the charging device 12 according to this second embodiment is configured such that the opening ratio along the longitudinal direction L of the grid electrode 122 is uniform by narrowing the line width of the connecting portions 122g, 122g, ... in areas where the arrangement density is high and widening the line width of the connecting portions 122g, 122g, ... in areas where the arrangement density is low, depending on the arrangement density of the multiple connecting portions 122g, 122g, ...

[0135] The aperture ratio of the grid electrode 122 does not need to be strictly constant along the longitudinal direction L, and it is desirable that the aperture ratio of the grid electrode 122 be uniform within the range of 86 to 95%.

[0136] In the charging device 12 according to the second embodiment, the grid electrode 122 is configured so that the aperture ratio along the longitudinal direction L is uniform. Therefore, by providing the grid electrode 122 with a plurality of connecting portions 122g, 122g, ..., it is possible to suppress fluctuations in the aperture ratio of the grid electrode 122 and fluctuations in the charging performance along the longitudinal direction L.

[0137] The other configurations and operations are the same as those of the first embodiment, and therefore the description thereof will be omitted.

[0138] Embodiment 3 17 is a structural diagram showing a charging device according to a third embodiment of the present invention. The charging device according to the third embodiment is configured such that the control electrode is divided into an increased number of segments along a direction intersecting the direction of rotation of the body to be charged, and the line widths of the multiple connecting portions in each segment are made different.

[0139] 17, the charging device 12 according to the third embodiment is configured such that the grid electrode 122 is divided into five equal parts along the longitudinal direction, and thus divided into five regions. The grid electrode 122 has a central portion 400 located in the center along the longitudinal direction, end regions 401 and 402 located at both ends along the longitudinal direction, and intermediate regions 403 and 404 located between the central portion and both ends.

[0140] For the sake of convenience, we will explain the case where the grid electrode 122 is divided into five equal parts along the longitudinal direction, but in an actual charging device, it is preferable to divide it into approximately 30 equal parts along the longitudinal direction in order to achieve a uniform aperture ratio.

[0141] 17 , in the charging device 12 according to the third embodiment, for example, a plurality of connecting portions 122g, 122g,... are arranged on the grid electrode 122 so that 50 of them have a line width of 0.8 mm in the region of the center portion 400, 30 of them have a line width of 1.3 mm in the regions of the intermediate portions 403 and 404, and 15 of them have a line width of 2.7 mm in the regions of the end portions 401 and 402. As a result, because the lengths of the connecting portions 122g, 122g,... are constant, the area (aperture ratio) occupied by the connecting portions 122g, 122g,... by providing the plurality of connecting portions 122g, 122g,... can be kept approximately constant by simple calculation: 50×0.8=40, 30×1.3=39, 15×2.7=40.5.

[0142] The vibration suppression effect of the grid electrode 122 is more influenced by the arrangement density than by the line width of the multiple connecting portions 122g, 122g, ..., so even if the line width of the multiple connecting portions 122g, 122g, ... is changed, the impact on the vibration suppression effect is so small that it can be ignored.

[0143] The other configurations and operations are the same as those of the first embodiment, and therefore the description thereof will be omitted.

[0144] Embodiment 4 18 is a structural diagram showing a charging device according to a fourth embodiment of the present invention. The charging device according to the fourth embodiment is configured such that the multiple connecting portions of the control electrode are not arranged along the direction of rotation of the body to be charged, but are arranged at an angle with respect to the direction of rotation of the body to be charged.

[0145] That is, as shown in FIG. 18, the charging device 12 according to this embodiment 4 is configured such that the multiple connecting portions 122g, 122g, ... that connect the linear conductors 122f, 122f, ... that make up the grid electrode 122 are arranged at an angle with respect to the width direction W of the charging device 12, which is the rotation direction of the photosensitive drum 11.

[0146] To explain further, in the charging device 12 according to the fourth embodiment, as shown in FIG. 18, the start points and end points of the multiple connecting portions 122g, 122g, . . . are arranged so that they do not overlap.

[0147] If the multiple connecting portions 122g, 122g, ... that connect the linear conductors 122f, 122f, ... that make up the grid electrode 122 are arranged so that their starting points and ending points overlap, the points where these starting points and ending points overlap may become ``nodes'' of vibration, and new vibrations may be generated.

[0148] Therefore, in the charging device 12 according to this fourth embodiment, by arranging the multiple connecting portions 122g, 122g, ... so that the starting points and ending points do not overlap, it is possible to prevent or suppress the multiple connecting portions 122g, 122g, ... from becoming "nodes" of vibration and generating new vibrations.

[0149] The other configurations and operations are the same as those of the first embodiment, and therefore the description thereof will be omitted.

[0150] (Addendum) (((1))) A discharge electrode; a control electrode disposed between the discharge electrode and a body to be charged by the discharge electrode; Equipped with The control electrode is a plurality of linear conductors arranged so as to intersect with the rotation direction of the body to be charged at an arbitrary angle; a plurality of connecting portions which are members connecting the linear conductors along the rotation direction of the body to be charged, and which are arranged more in a central region than in both end regions in a direction intersecting the rotation direction of the body to be charged; A charging device having (((2))) A discharge electrode; a control electrode disposed between the discharge electrode and a body to be charged by the discharge electrode; Equipped with The control electrode is a plurality of linear conductors arranged so as to intersect with the rotation direction of the body to be charged at an arbitrary angle; a plurality of connecting portions which are members connecting the linear conductors along the rotation direction of the body to be charged, and which are arranged in a facing region where the discharge electrode and the control electrode face each other in greater numbers than in a non-facing region where the discharge electrode and the control electrode do not face each other in the rotation direction of the body to be charged; A charging device having (((3))) The charging device according to (((1))), wherein the plurality of connecting portions connect adjacent ones of the plurality of linear conductors to each other. (((4))) The plurality of connecting portions are The charging device described in (((3))) is arranged so that the density of the connecting portions is highest in a central region of the control electrode in a direction intersecting the rotation direction of the charged body, and the density of the connecting portions increases stepwise toward both ends of the control electrode. (((5))) The charging device according to ((1)), wherein the plurality of connecting portions are arranged including a non-opposing region where the discharge electrode and the control electrode do not face each other. (((6))) The plurality of connecting portions are The charging device described in (((5))) is arranged so that the density of connecting portions in an opposing region where the discharge electrode and the control electrode are opposed to each other is higher than the density of connecting portions in a non-opposing region where the discharge electrode and the control electrode are not opposed to each other in a direction intersecting the rotation direction of the charged body. (((7))) The charging device according to (((1))), wherein the control electrode has a uniform aperture ratio along a direction intersecting with the direction of rotation of the body to be charged. (((8))) The plurality of connecting portions are The charging device according to (((7))), wherein the line width of the connecting portion at the center of the control electrode is narrower than the line width of the connecting portion at both end regions in a direction intersecting the rotation direction of the body to be charged. (((9))) The charging device according to (((1))), wherein a plurality of the discharge electrodes are arranged along the rotation direction of the body to be charged. (((10))) The charging device according to (((9))), wherein the discharge electrode has a voltage applied to the most upstream side along the direction of rotation of the body to be charged that is higher than the other sides. (((11))) A charging device according to any one of (((1))) to (((10))), An image forming unit that is detachably attached to an image forming apparatus. (((12))) Image holding means; a charging means for charging the surface of the image holding means; an electrostatic latent image forming means for forming an electrostatic latent image on the surface of the image holding means charged by the charging means; Equipped with An image forming apparatus using the charging device according to any one of ((1))) to (((10))) as the charging means.

[0151] According to the charging device of (((1))), the occurrence of uneven charging due to vibration of the control electrode can be suppressed compared to when the multiple connecting parts that make up the control electrode are evenly arranged along the axial direction. According to the charging device of (((2))), the occurrence of uneven charging due to vibration of the control electrode can be suppressed compared to when the multiple connecting portions constituting the control electrode are arranged in equal numbers in the non-opposing area where the discharge electrode and the control electrode do not face each other and in the opposing area where the discharge electrode and the control electrode face each other. According to the charging device of (((3))), vibration of the linear conductors can be suppressed compared to when adjacent linear conductors among the linear conductors are not connected to each other. According to the charging device of (((4))), the occurrence of vibration in the linear conductor can be effectively suppressed compared to when the multiple connecting parts are arranged so that the density is equal in the central region of the control electrode and the regions at both ends of the control electrode in a direction intersecting the rotation direction of the charged body. According to the charging device of (((5))), the vibration of the linear conductor can be effectively suppressed compared to when multiple connecting portions are arranged only in the opposing area where the discharge electrode and the control electrode face each other. According to the charging device of (((6))), the multiple connecting portions can effectively suppress vibration of the linear conductor compared to when the density of the connecting portions in the non-opposing areas where the discharge electrode and control electrode do not face each other in the direction intersecting the rotation direction of the charged body is equal to the density of the connecting portions in the facing areas where the discharge electrode and control electrode face each other. According to the charging device of (((7))), the control electrode can suppress unevenness in the charging potential along the axial direction of the charged body, compared to when the aperture ratio along the axial direction of the charged body is different. According to the charging device of (((8))), the aperture ratio of the multiple connecting portions can be easily set compared to when the line width of the connecting portions in the regions at both ends of the control electrode in the direction intersecting the rotation direction of the charged body is equal to the line width of the connecting portion in the central portion. According to the charging device of (((9))), charging ability can be improved compared to when a single discharge electrode is used. According to the charging device of (((10))), the discharge electrode can improve the charging characteristics of the body to be charged compared to when the applied voltage is set high except for the most upstream side along the rotation direction of the body to be charged. According to the image forming unit of (((11))), the occurrence of uneven charging due to vibration of the control electrode can be suppressed compared to when the image forming unit does not have a charging device described in any of (((1))) to (((10))). According to the image forming apparatus of (((12))), the occurrence of uneven charging due to vibration of the control electrode can be suppressed, and image quality can be improved, compared to when the charging device described in any of (((1))) to (((10))) is not used as the charging means. [Explanation of symbols]

[0152] 1...Image forming device 12...Charging device 120...Shield case 121...Discharge wire 122...Grid electrode 122a...control unit 122b,c…Connection part 122f...Straight conductor 122g…Connection part

Claims

1. A discharge electrode; a control electrode disposed between the discharge electrode and a body to be charged by the discharge electrode; Equipped with The control electrode is a plurality of linear conductors arranged so as to intersect with the rotation direction of the body to be charged at an arbitrary angle; a plurality of connecting portions which are members connecting the linear conductors along the rotation direction of the body to be charged, and which are arranged more in a central region than in both end regions in a direction intersecting the rotation direction of the body to be charged; A charging device having

2. A discharge electrode; a control electrode disposed between the discharge electrode and a body to be charged by the discharge electrode; Equipped with The control electrode is a plurality of linear conductors arranged so as to intersect with the rotation direction of the body to be charged at an arbitrary angle; a plurality of connecting portions which are members connecting the linear conductors along the rotation direction of the body to be charged, and which are arranged in a facing region where the discharge electrode and the control electrode face each other in greater numbers than in a non-facing region where the discharge electrode and the control electrode do not face each other in the rotation direction of the body to be charged; A charging device having

3. The charging device according to claim 1 , wherein the plurality of connecting portions connect adjacent ones of the plurality of linear conductors to each other.

4. The plurality of connecting portions are 4. The charging device according to claim 3, wherein the density of the connecting portions is highest in a central region of the control electrode in a direction intersecting the rotation direction of the body to be charged, and the density of the connecting portions is gradually decreased toward both ends of the control electrode.

5. 2. The charging device according to claim 1, wherein the plurality of connecting portions are arranged to include a non-opposing region where the discharge electrode and the control electrode do not face each other.

6. The plurality of connecting portions are 6. The charging device according to claim 5, wherein the density of connecting portions in an opposing region where the discharge electrode and the control electrode are opposed to each other is higher than the density of connecting portions in a non-opposing region where the discharge electrode and the control electrode are not opposed to each other in a direction intersecting the rotation direction of the body to be charged.

7. 2. The charging device according to claim 1, wherein the control electrode has a uniform aperture ratio along a direction intersecting the direction of rotation of the member to be charged.

8. The plurality of connecting portions are 8. The charging device according to claim 7, wherein the line width of the connecting portion at the center of the control electrode is narrower than the line width of the connecting portion at both end regions in a direction intersecting the direction of rotation of the member to be charged.

9. 2. The charging device according to claim 1, wherein a plurality of the discharge electrodes are arranged along the rotation direction of the member to be charged.

10. 10. The charging device according to claim 9, wherein the discharge electrode has a voltage applied to the most upstream side along the direction of rotation of the member to be charged that is higher than the other voltages.

11. A charging device according to any one of claims 1 to 10, An image forming unit that is detachably attached to an image forming apparatus.

12. Image holding means; a charging means for charging the surface of the image holding means; an electrostatic latent image forming means for forming an electrostatic latent image on the surface of the image holding means charged by the charging means; Equipped with An image forming apparatus using the charging device according to any one of claims 1 to 10 as the charging means.

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